The overall objective of this research proposal is to define the role of cyclic GMP in nervous tissue. Our secific aims are: 1. To determine the relationship of cyclic GMP to neurotransmission with particular emphasis on a) attempting to define which of the putative neurotransmitter systems are associated with cyclic GMP metabolism and b) attempting to determine in which component of the neurotransmission mechanism cyclic GMP is involved. 2. To attempt to determine what effects cyclic GMP has on neural function and metabolism. 3. To further characterize the biochemical processes involved in cyclic GMP formation, maintenance and degradation in nervous tissue. 4. To develop a more sensitive assay method for measuring cyclic AMP and cyclic GMP in tissues. It is anticipated that achievement of the above goals will result in a better understanding of neurochemical and neuropharmacological mechanisms. This, in turn, should lead to a more rational use of therapeutic agents in the treatment of nervous disorders.